Cressall
INDUSTRIAL
POWER
RESISTORS
Neutral Earthing
Dynamic Braking
Harmonic Filters
Portable Load Units
Load Banks
Motor Control
WHY SPECIFY CRESSALL RESISTORS?
2
THE WORLD’S FOREMOST RESISTOR MANUFACTURER, Cressall Resistors offer an
unrivalled combination of experience and the widest range of resistor technologies.
Cressall Resistors have almost 100 years experience of
producing power resistors for use in the electro-technical
market. With design and manufacturing facilities at two
locations in the UK, Cressall can supply both standard
and custom-designed resistor solutions for any application from a few watts up to several megawatts and for
operation at any voltage.
With more than 100 employees at facilities in
Leicester and Dereham, Norfolk, our qualified
engineers will advise you on the most suitable and
competitive design for your requirements.
A quality management system approved to ISO9001
combined with the continuous development of our
products and the people that provide them ensure that the
service we offer is second to none.
With sister companies and distributors around the world
Cressall can provide global customer service.
Details of our sister companies and distributors can be
found on our website www.cressall.com.
3
WHY SPECIFY CRESSALL RESISTORS?
Cressall reliability
Cressall products are well-proven in the most arduous
and demanding environments such as found in steel works,
chemical plants and oil rigs.
Versatile technology
The broad range of Cressall resistor elements provides the
versatility required to offer solutions for any application.
Resistors can be specified for any combination of
resistance value, temperature rise, duty cycle, current and
voltage rating.
Product development and innovation
Cressall’s range of resistor elements are subject to
a process of continuous research, development and
product innovation.
4
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Neutral Earthing
6
Earth Fault Detection 11
Recent developments include:
• Merger of TPR Resistors business with Cressall Resistors
• Opening of a transit and special projects office in
Harmonic Filters
18
Portable Load Units 20
marine use
• Portable load bank range extended with 6kW and 100kW
12
Dereham, Norfolk
• Launch of a range of water-cooled braking resistors for
Dynamic Braking
AC units
• Next-day despatch service for standard braking resistors
Fast response
Static Load Banks
22
Expanded Mesh
24
Edgewound26
Whatever your resistor requirements our team of
RP Coils
27
qualified engineers and production staff will offer a fast, cost-
ZO Coils
28
effective solution and deliver a service that is second to none.
ZC Coils
29
This commitment extends through every stage of the
CS Coils
30
process, from initial enquiry to after-sales support.
Service Grids
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Quality control
Cressall Resistors has produced
products under a quality control
system, approved to ISO9001.
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GP Coils
33
CC Coils
34
5
neutral earthing
neutral
earthing
Cressall neutral earthing resistors (NERs) are
The rating of an NER is chosen to meet the
employed in AC distribution networks to limit
requirements of the system protection scheme;
the current that would flow through the neutral
this will include consideration of maximum
point of a transformer or generator in the event
acceptable fault current, earth potential levels,
of an earth fault.
and preventing damage caused by the fault.
Resistors rated 77kV, 400A for 15
seconds supplied by Cressall are being
used in domestic Japanese substations.
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Cressall NERs have numerous benefits:
Choice
Stability and predictability
An extensive range of metal resistor elements
The resistance value is set at the manufacturing
allows selection of the most efficient and cost
stage and remains constant throughout the life
effective solution for any required duty. Cressall
of the NER. Unlike liquid resistors, changes in
can manufacture NERs for any system voltage
resistance value due to the fluctuations in ambient
and initial current with rated times from a few
temperature are negligible. This means that pro-
seconds to continuous.
tection levels can be accurately pre-determined.
In contrast to an earthing reactor, a Cressall NER
does not induce phase changes or resonances into
the fault current and does not require matching
to the associated transformer.
Rapid cooling and short time ratings
Neutral Earthing
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
Edgewound26
Modern protection systems typically clear faults
in less than a second. However, the time rating of
Service Grids
31
an NER usually needs to cater for the possibility
of several successive faults.
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Cressall resistors cool down much faster than
liquid resistors after operation. To cater for
successive faults liquid resistors have longer time
ratings, typically 30 seconds, as opposed to 10
seconds for metallic resistors.
Ease of installation
Cressall NERs are compact and do not require site
calibration or auxiliary power supplies.
Low operating costs
Fixed resistance values mean that maintenance
is limited to periodic inspection and cleaning.
Anti-frost and anti-condensation heaters are not
generally required.
Reliability
NERs may only be called upon to operate a few
times in their service life, which may be 25 years
or more. Cressall NERs have been proven reliable in numerous installations and under severe
climatic conditions world-wide.
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neutral
earthing
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Construction
Standards
At present the only standard for NERs is ANSI/IEEE
The tie-rods are supported between galvanised
Std 32, 1972. Cressall NERs can be designed and
end-plates to form banks. These banks can be
tested to comply with this standard, or with in-
mounted on top of each other with intermediate
dividual client specifications.
insulators to form a complete self-supporting
stack.
Resistor elements
For the majority of ratings the most suitable
element is the type RP oval edge-wound coil.
Interconnections between coils are copper,
using two bolts per joint.
RP resistors are manufactured from a continu-
Enclosure protection ratings
ous stainless steel strip, wound edgewise into
The standard enclosure is designed to IP23 to
oval coils. Each coil is supported by ridged
IEC529 (to prevent the ingress of foreign bodies
ceramic insulators mounted on a stainless steel
greater than 12mm, and rain falling at any angle
centre support, with stainless steel terminals
up to 60° from the vertical). This rating is suit-
welded at each end. This arrangement allows
able for indoor or outdoor use as it allows suf-
free expansion and contraction at operating tem-
ficient cooling and provides more than adequate
peratures up to 1100°C without imposing strain
protection unless the environmental conditions
on the assembly.
are extreme. Protection ratings above IP23 are
The resistance alloys used are high temperature
stainless steels capable of withstanding temperature excursions to 1100°C whilst retaining their
strength, unlike 304 or other structural grade
stainless steels which are limited to much lower
temperatures.
NERs designed for operation to higher temperatures require less active mass, resulting in more
compact and economical designs.
rarely needed because Cressall resistor stacks
are virtually corrosion proof and immune from
progressive pitting and rusting. The operation of
the resistor and the ceramic insulators are not
affected by exposure to condensation, sand or
fine dust, provided that the dust is not unduly
conductive.
If higher degrees of protection are specified,
these can be provided (up to IP55). It should be
realised that the operational penalty of using less
Temperature coefficient of resistance
well ventilated enclosures is that the external
Unlike structural grade stainless steels the tem-
surfaces will become hotter and cooling times
perature coefficient of the material used ensures
will be longer.
a resistance increase of less than 3.5% per 100°C
rise over the operating temperature range.
Enclosure materials and finish
Enclosures are manufactured as standard from
Resistor banks
unpainted stainless steel. This ensures better and
The end insulators of individual resistor ele-
more economic long term corrosion protection
ments are clamped and locked on to tie-rods. Any
than galvanised or painted mild steel units.
element can be removed without disturbing the
If required other enclosure materials and
remainder.
special finishes can be supplied to comply with
users’ specifications.
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Neutral Earthing
Electrical connections
Earth Fault Detection 11
As standard a HV bushing is mounted on the
As an alternative to the cable boxes, bushings
side of the enclosure. The bushing is housed in
can be mounted on the top cover. However, the
an air insulated bottom-entry cable box with a
enclosure should then be mounted on a plinth
removable undrilled gland plate.
or structure to raise the height of the bushing to
A low voltage bushing is provided for the resistor
earth connection. Where required this can also be
enclosed in a cable box. Earthing of the enclosure
Dynamic Braking
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Harmonic Filters
18
a suitable distance above ground level to avoid
accidental contact. Suitable steel plinths can be
Portable Load Units 20
supplied.
is via two separate stud type terminals, fitted
Static Load Banks
22
Expanded Mesh
24
diagonally opposite each other.
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Service Grids
Eyebolts
for lifting
Rain
shedding roof
HV cable box
(to IP54) for neutral
connection
Provision for
current transformers,
isolators, etc as
required
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Standard
enclosure to
IP23 or IP54
Stainless steel
type RP resistor
elements
All primary
and secondary
insulators are
ceramic
Undrilled
gland plate
Double bolted
interconnections
Separate
enclosure earth
Standard enclosure either unpainted
stainless steel or polyester powder
coated mild steel
LV earth
connection
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neutral
earthing
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Other equipment
Where required cable boxes can house current
transformers, isolators, vacuum contactors or
other ancillary equipment.
Standard tests
As standard, NERs are tested to the requirements
of ANSI/IEEE Std 32, 1972.
Routine tests on all units include:
• Dimensional check to relevant drawing
• Resistance measurement at ambient temperature
• One minute power frequency withstand test to levels specified in ANSI/IEEE Std 32, 1972 typically (2.25 x line voltage) +2kV
Temperature rise type tests have been carried
out on a range of typical ratings for both 760°C
(in accordance with ANSI/IEEE Std 32, 1972) and
1000°C. Copies of these results are available.
NER rated 11kV, 625A for 10 seconds
installed in a substation near Heathrow.
Transformer mounted NER rated
11kV, 1000A for 10 seconds.
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Neutral Earthing
6
Earth Fault Detection
Dynamic Braking
12
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
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Service Grids
31
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Cressall Earth Fault
Detection systems
• Compact
The earth fault detection resistor is connected
• Designed to be retrofitted
between the neutral point of the distribution network
• Options for indication, metering, pulsing and auxiliary resistance circuits
and earth. In the event of an earth fault the resistor
In low voltage three phase distribution networks
where continuity of supply is a priority, high
resistance earthing reduces the risk of service
will limit the fault current to a few amps (typically
3-5). Control equipment continuously monitors
this earth current and provides indication when it
exceeds a predetermined level.
interruptions caused by an earth fault while main-
Units can be supplied with a range of features:
taining the integrity of the system.
• Earth fault protection and monitoring
Where their use is permitted, Cressall earth fault
• Pulsed earth fault protection and hand held detection resistors are ideal for sensing and
locating earth faults quickly, minimising plant down
• Double resistor paths with continuous
time in industrial applications.
sensor for easy fault finding
monitoring for fail safe protection
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DYNAMIC BRAKING
DYNAMIC
BRAKING
Cressall is one of the leading suppliers of
braking torque produced and thus the rate at
dynamic braking resistors to OEMs, integra-
which the motor will stop, the lower the resistance
tors, users and distributors of AC variable
the higher the braking torque and the quicker the
frequency drives.
stop. Drive manufacturers will specify a minimum
Cressall DBRs are used to stop motors or to
resistance value to ensure that the braking
produce a braking torque in the motor during overhauling load conditions. The dynamic
braking resistor is connected across the DC
capacity of the drive is not exceeded. As standard Cressall manufacture DBRs with a –0/+10%
tolerance to ensure optimum performance (other
bus and can see voltages as high as 1100 volts
values can be achieved if required).
(Cressall DBRs can be insulated and rated for
When sizing brake resistors, key parameters for
higher voltages if required).
consideration are resistance value, braking power
The resistance value determines the amount of
and the duration and frequency of the stop.
Braking resistors are used
for speed control and braking
of passenger lifts.
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Neutral Earthing
Construction
Manufactured using electrical grade alloys,
Type ZC edgewound strip
resistor elements are either type ‘ZC’ (coiled strip)
•
Low to medium resistance value
•
High power intermittent duty
•
High overload capacity
‘CC’ (coiled coil) or ‘SD’ (expanded mesh). Units
can be supplied as loose elements, open banks
or housed in ventilated enclosures.
Type CC coiled coil resistors
•
Medium to high resistance value
•
Rapid duty cycle
•
High overload capacity
6
Earth Fault Detection 11
Dynamic Braking
Harmonic Filters
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Type SD expanded mesh
•
Low resistance value
•
High continuous power
•
Rapid duty cycle
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
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Service Grids
31
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DYNAMIC
BRAKING
Standard dynamic braking resistors
To meet the requirements of the market Cressall
have developed a range of standard DBRs
designed to cater for the most common applications. Depending on rating these units can be
manufactured from stock components or (for the
most popular sizes) supplied direct from stock.
As standard Cressall DBRs are housed in plated
mild steel enclosures affording ingress protection to IP20 or IP21. They include a built-in
terminal box, terminal block and high temperature wiring. A normally closed thermal switch
is fitted as standard. Units may be wall or roof
mounted as required.
• Most common sizes available
from stock
• Easily installed
• Suitable for all ranges of drives
• Suitable for any power or duty cycle
• Insulated for operation at 800V
• Thermal trip fitted as standard
• CE marked
A DBR used for hoist
application undergoes final
testing before installation.
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Neutral Earthing
6
Earth Fault Detection 11
Dynamic Braking
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
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Designed for easy panel mounting,
DBRs are used in a range of industries
such as food processing and lift control.
Service Grids
31
Wirewound32
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DYNAMIC
BRAKING
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ES braking resistors
Duty cycle and power
A comprehensive range of compact, IP20 dynamic
The eight standard enclosures have continuous
braking resistors with a choice of accessories
power ratings from 0.6kW to 8kW. These ratings
that keeps both purchase and installation costs
can be exceeded when power is applied for less
low - all available at short notice.
than 100% of the time. The graph below gives
• Rated for repetitive duty
a “power multiplier” based on a 10 second “on
• Resistance never lower than expected
• Robust construction
time”. Multiply the resistor’s continuous rating by
the “power multiplier” number to calculate power.
Example: 10 seconds on in 100 seconds is defined
• Low inductance element
as a 10% duty cycle. A 10% duty cycle gives a 4.6
• High overload capacity
times power multiplier. ES1 resistors are rated
• Close tolerance (+5% - 0%)
1.5kW continuously and so can be rated 6.9kW
• Noise free
• Temperature stable element
(4.6 x 1.5kW) for 10 seconds in 100 seconds. If
the resistors have a resistance of 100Ω or more,
then the power rating is reduced by 20%.
Cressall ES braking resistors are based on HP
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Coils, spiral wire-wound on ceramic formers.
8
and cool rapidly. The resistance material is a
high grade stainless steel with no more than 7%
resistance increase over the whole temperature
range. Cheaper designs using 304 stainless steel
can increase in resistance during the heating cycle
Power Multipler
These elements have a high overload capacity
7
6
5
4
3
2
1
0
1
2
3
4
5
6 7 8 9 10
by as much as 50%, which results in lower current
and less effective braking.
The enclosures are made of galvanized steel.
Ingress protection is IP 20.
Options are a thermal switch and/or terminal
cover.
Applications
• Dynamic braking
• Motor control
• Variable speed drives
• Lifts & elevators
• Cranes & winches
• Conveyors
• Test loads
16
20
30
40 50 60 70
Percentage duty cycle
Enclosure
ESH
EST
ES1 EST2 ES2
ES3
ES4
ES8
Continuous
power/kW
0.6
1.0
1.5
2.0
3.0
4.5
6.0
8.0
Min Ω
2.5
4.0
6.0
2.0
3.0
2.0
1.5
0.75
Max Ω
180
300
450
600
900 1350 1800 3600
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Maximum operating voltage:
Thermal sensor (optional)
1000V DC or AC rms
Located near screw terminals
Neutral Earthing
6
Earth Fault Detection 11
Normally closed contact,
Connections
Power: Screw terminals for up to 10mm2 cable
(ESH-ES3), M8 stud terminals (ES4-8)
opens at ~250˚C,
Dynamic Braking
re-closes at ~210˚C
Harmonic Filters
Voltage: 240V AC rms;
Earth: Self tapper, near screw terminals
Thermal sensor: 6.25mm male blade (faston)
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current: 7A AC rms
Portable Load Units 20
Installation
connections (receptacles not supplied)
Terminal cover (optional for ESH-ES3)
Two 20mm gland holes with cover grommets
provided on end face.
Units have slotted mounting points suitable for
Static Load Banks
22
Expanded Mesh
24
M6 fixings. Mount horizontally with base facing
down. Other orientations may result in increased
element temperatures.
The cover overhangs the
Warning: Units must never be mounted with the terminal
area or base uppermost.
resistor by 22mm. The
open overhang area can
Edgewound26
Service Grids
be used for cable entry.
31
Wirewound32
ESH
EST
ES2
ES1
ES3
EST2
ES4
ES8
A
Mounting dimensions (mm) and weights
C
D
E
kg
236
121
92
141
1.4
EST
367
315
121
92
141
1.8
ES1
467
415
121
92
141
2.2
EST2
367
315
213
185
141
3.0
ES2
467
415
213
185
141
3.8
ES3
467
415
307
278
141
5.4
ES4
500
422
380
352
195
6.6
ES8
500
422
380
352
390
11.5
C
D
B
288
B
E
A
ESH
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HARMONIC FILTERS
HARMONIC
FILTERS
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The ever-increasing use of power electronics has
led to a rise in the amount of harmonic voltages
on the power supply network. Harmonics can
have an adverse impact on many electrical
systems and, as such, this makes the aspect of
power quality more and more important for both
suppliers and users of electrical power.
These harmonic voltages can increase line losses
and also have a detrimental effect on other
users of the network.
Harmonics can be reduced to acceptable levels
by passive filter circuits consisting of inductors,
capacitors and resistors. The filter circuit allows
through the fundamental frequency and diverts
the harmonic frequencies to the resistor bank
where they are dissipated as heat and thus lost
from the system.
Low inductance is a key design feature of filter
resistors. The units offered by Cressall have
negligible inductance and are particularly suitable
for operation at high voltages in the following
applications:
Static VAr compensators (SVCs)
HVDC transmission systems
Mechanically switched capacitor
damping networks (MSCDNs)
Industrial harmonic filters
Cressall have supplied resistors for use within
filter systems at every level of the electrical
distribution system, from 400kV grid transformers
to 415V industrial equipment, and with power
ratings from a few watts to several megawatts.
125kV BIL damping resistors
installed as part of the upgrade to
the West Coast Main Line.
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Roof mounted damping and discharge
resistors used as part of a relocatable
Static VAr Compensator.
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Neutral Earthing
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
Edgewound26
Service Grids
31
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Used by the National Grid
Company, these filter
resistors are rated 550kV
BIL, 500kW per phase.
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PORTABLE LOAD units
PORTABLE
LOAD units
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24-28 DC Model
Model typeVoltage
(V)
DC110
28V
48-54 DC Models
Model typeVoltage
Power
(kW)
Steps
Continuous
current (A)
3.3
fully variable
120
Power
(kW)
Steps
Continuous
current (A)
Dimensions
L x W x H (mm)
400
200
500
Dimensions
L x W x H (mm)
Weight
(kg)
10
Weight
(kg)
DC70
50V
3.5
fully variable
70
400
200
500
10
DC220
50V
11.0
fully variable
210
540
310
500
15
DC600
50V
30.0
fully variable
600
560
400
840
40
Units are each supplied with a pair of leads
•Fully variable current setting
•Cooling fan driven by test load
AC Models
Model typeVoltage
(V)
•Shunt for current measurement with 4mm
banana sockets (all units except DC600)
Power
(kW)
Steps
W(A)
Continuous
current (A)
Dimensions
L x W x H (mm)
Weight
(kg)
AC6
220-240, 1Ø
6
333
27
495
220
415
10
AC6 Dual
110-120, 1Ø
6
333
54
495
220
550
12
220-240, 1Ø
560
400
840
30
1150 700
800
140
27
AC30*
220-240, 1Ø
15
333
62
380-415, 3Ø
30
1000
41
AC 100
220-240, 1Ø
33
400
150
380-415, 3Ø
100
1250
AC6 includes one (AC6 Dual Voltage: two) 1.5m long cable complete with IEC 60309-2 connectors - hard wired into the unit.
AC30 includes either a single or a three phase lead. Unless specified at time of order a three phase lead will be included
automatically.
AC100 includes four female connectors to be fitted to customers’ own cables, to match the male connectors on the unit.
•Cooling fan driven by test load
•Illuminated switches
•Ability to set unbalanced loads
•Single and three phase operation in one unit
•Input connectors to BS4343/
DIN49462
•DIN 48mm voltmeter, ammeter and
frequency meter
AC/DC Model
Model typeVoltage
(V ac or dc)
Power
(kW)
Steps
W(A)
Continuous
current (A)
Dual30 (120/240) 120
31.5
31.5500(2) 131
240
500(4)
262
Dimensions
L x W x H (mm)
Weight
(kg)
600500800
50
Units are each supplied with a pair of leads
•Full power at two voltages in a
single unit
•DIN 48mm voltmeter, ammeter
and separate 1.5% shunt
20
•Single phase ac or dc operation
•Contactor switched
•Fans and contactors driven by external 110V
or 230V ac supply
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Cressall’s range of standard units is designed for
testing ac and dc systems, including batteries,
uninterruptible power supplies (UPSs) and standby generators.
Neutral Earthing
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
All units are fan-cooled, which helps to ensure a
compact design. The fan supply is taken from the
test load itself or from an auxiliary supply of 110
or 230V ac, according to model.
Portable Load Units
Units are fitted with over temperature protection.
To reduce weight enclosures are manufactured
from aluminium and fitted with handles and
where required have castors to ease manoeuvrability. Load banks are supplied with one
cable and connector.
DC and AC/DC models can be operated at voltages
lower than their nominal rating. Power is reduced
accordingly.
Static Load Banks
22
Expanded Mesh
24
Edgewound26
Service Grids
31
Wirewound32
21
STATIC
LOAD BANKS
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Naturally cooled load banks
•
High reliability
•
Virtually silent operation
•
No moving parts
•
No auxiliary supplies
•
Minimal maintenance
•
Any power rating
A naturally ventilated load
resistor rated 86MW at 13.8kV
installed in Canada and used for
testing gas turbines.
22
Cressall can offer load banks that are cooled by
natural convection.
These are virtually silent in operation and with
no moving parts are extremely reliable, requiring minimal maintenance. Auxiliary supplies are
generally not required.
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Neutral Earthing
Force cooled load banks
compact alternative to naturally cooled units.
•
Compact design
•
Cost effective
•
Optional infra-red thermal protection
thermal sensors and air pressure switches for
•
Any power rating
protection.
Acoustic attenuation can be provided to meet
specified noise levels. Units are supplied with
Cressall can offer force cooled load units. At
All units can be supplied with switchgear and
higher powers these provide a cost effective and
instrumentation if required.
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
Expanded Mesh
24
Edgewound26
Service Grids
31
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Rated 7MW at 13.8kV this force
cooled load resistor is used for
testing generators in Germany.
Force cooling or natural ventilation
Suitable for any power and any voltage (ac or dc)
Single or multiple sections
23
Technologies
EXPANDED
MESH
Versatility
Light weight
Cressall engineers can select expanded mesh with
Expanded mesh elements and their mountings
any configuration of element length, cross-sec-
are lighter in weight per kilowatt than any other
tion, material thickness, banking arrangement and
known type.
cooling method to suit the requirements of the
application.
Expanded mesh resistors can be made from any
suitable resistance material. As standard Nickelchrome and iron-chrome-aluminium alloys are
Negligible inductance
In tests up to 1MHz, expanded mesh resistor
elements have been demonstrated as non-inductive for all normal practical purposes.
used. The selection is based upon cost, temperature
Durable construction
coefficient of resistance and magnetic properties.
Expanded mesh elements are robust and ca-
Excellent heat dissipation
Expanded mesh elements provide a very large
surface area relative to mass, giving excellent
heat transfer capabilities and making them ideal
pable of withstanding vibration, yet sufficiently
flexible for shock absorption.
Elements have the advantage of fixed mountings:
movement due to thermal expansion is absorbed
for continuous duties.
within the mesh structure itself.
The active material, insulators and mountings
Although the heated part of the element and the
on expanded mesh resistor elements are
designed to maximise the use of convecting air
for ventilation. An unrestricted path through
metal supporting it are formed from a single
sheet, heat is kept out of the mountings, terminations and supporting insulators to a much greater
the active material avoids ‘hot spots’ and local
extent than with other designs.
overheating.
Primary insulation consists of micanite tubes and
Expanded mesh resistor elements cool from
mica washers. Secondary insulation consisting of
600°C to almost ambient temperature in approximately one-eighth of the time taken by an
average grid. This means that expanded mesh
resistors are also suitable for continual ‘on/off ’
cycles, making full use of the ‘off ’ periods for
rapid cooling.
24
www.cressall.com
ceramic insulators may be added to permit operation at any required voltage level.
www.cressall.com
Neutral Earthing
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
Edgewound26
Service Grids
31
Wirewound32
Non-corrodible
resistance girder
End insulation
mica washers
Steel tie-rod
Mica
insulating
tube
Spigotted bush
assembly
Inter-girder
insulation
mica washer
Steel spacing bush
protecting mica
tube assembly
25
Technologies
EDGEWOUND
RESISTORS
www.cressall.com
Edgewound coils
•
Versatile and robust
•
Good heat dissipation
•
High overload capacity
•
Standard coil sizes
•
Standard banking designs
Cressall’s edge-wound coiled strip resistors are an
efficient way to package a large resistance mass
into a small space. The high mass and robust
design provides exceptional short-term overload
capacity.
Applications include:
•
Neutral earthing resistors
•
Dynamic braking
•
Motor starting and speed control
•
Load testing
Construction
All styles are manufactured from a continuous
Elements can be supplied either loose, as banked
stainless steel or copper-nickel strip wound edge-
assemblies or mounted in a range of standard
wise to form a coil which is then fitted on ridged
ventilated enclosures, according to customers
ceramic insulators and supported on a central
requirements.
steel support strap.
26
www.cressall.com
RP coils
Neutral Earthing
6
Manufactured from an oval wound stainless steel
Earth Fault Detection 11
strip the RP resistor is a very efficient method for
packaging a large resistor mass in a small volume.
One coil can hold up to 12kg of active resistor
Dynamic Braking
12
Harmonic Filters
18
material. RP coils are most commonly used in
neutral earthing and high energy motor control
applications.
Portable Load Units 20
Supplied either as loose coils or in banks up to twelve
coils wide and up to eight tiers high, they offer a
high degree of versatility to fit within any specified
envelope.
The resistor stacks are mounted on base insulators
and are self-supporting and free standing. This means
Static Load Banks
22
Expanded Mesh
24
Edgewound
that they can be easily incorporated in to customers
own enclosures when required.
Each coil is locked on to its supporting bank by
clamps and all the electrical connections between elements are made by double bolted copper
connections. This allows removal of an individual
RP Coils
27
ZO Coils
28
ZC Coils
29
CS Coils
30
Service Grids
element from the assembly without disturbing the
complete arrangement.
31
Wirewound32
RP stack dimensions
No. of
coils
Width
Mounting
overall (mm) centres (mm)
3
456
354
4
548
446
5
642
540
6
728
626
9
1002
12
1278
No. of
tiers
Height
(mm)
1
310
2
570
3
830
4
1090
5
1350
6
1610
7
1870
8
2130
900
1176
27
Technologies
EDGEWOUND
RESISTORS
www.cressall.com
ZO, ZC and CS coils
The ZO, ZC and CS styles of resistor are manufactured from edge wound stainless steel or coppernickel strip. They offer a wide range of resistance
values for medium current applications.
Units can either be supplied with fixed resistance taps or loose adjustable tapping clamps to
allow customer selection of the appropriate
ohmic value.
ZO coils
Insulated for operation up to 500V, ZO coils
offer the versatility of 108 different designs, each
of which can have its resistance set to any value
below its maximum.
ZO coils can be supplied either loose, as banked
ventilated enclosures, according to customers
assemblies or mounted in a range of standard
requirements.
ZO coil ratings
Continuous current (A)
for temperature rise of:
DC resistance
(Ω) ±10% (20°C ambient)
Style200°C265°C280°C375°C450°C ZO1ZO2ZO3 ZO4ZO5ZO6ZO7ZO8 ZO9
1
57
67
69
85
96
0.0270.0660.1090.1460.1850.2250.2650.3050.346
2
51
62
64
78
90
0.0370.0930.1520.2050.2600.3150.3650.42 0.48
337 45475968 0.052
0.130
0.210
0.285
0.36
0.44
0.51
0.59
0.67
434 43445665 0.070
0.170
0.280
0.385
0.49
0.59
0.69
0.80
0.91
528 33354349 0.102
0.256
0.415
0.57
0.72
0.87
1.01
1.18
1.34
623 27293643 0.133
0.332
0.540
0.735
0.93
1.13
1.32
1.52
1.74
720 24253237 0.176
0.440
0.720
0.985
1.24
1.50
1.76
2.03
2.31
8 17
21 22 27 32
0.200.500.801.101.381.681.972.262.57
9 15
17 19 24 28
0.300.751.201.652.082.522.963.503.86
10 12
15 16 21 24
0.401.001.602.202.783.353.944.525.15
11 10
12 14 18 21
0.581.271.972.663.364.064.755.456.15
12
11 12 16 18
0.731.602.483.354.235.115.986.867.73
28
9
Types ZO7, ZO8 and ZO9 are suitable for static equipment only
Dimensions (mm)
Dimensions (mm)
Coil lengthZO1ZO2ZO3ZO4ZO5ZO6ZO7ZO8ZO9
No. of coils
A115190265340410485560635710
C
228330431533635
B 95170245320390465540615690
D
254355457558660
2
3
4
5
6
www.cressall.com
ZC coils
Neutral Earthing
Designed for dynamic braking resistors ZC
Supported on M8 threaded rod, ZC ’s are
elements are similar in construction to the well
available in two lengths, they are insulated for
established ZO range.
operation at up to 800V and can be supplied loose,
mounted between end plates or housed in one of
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
our standard range of enclosures.
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
Edgewound
ZC coil ratings
DC resistance (Ω)
±10% (20°C ambient)
Continuous current (A)
for temperature rise of:
Style200°C265°C280°C375°C450°CZC5 ZC7
RP Coils
27
ZO Coils
28
ZC Coils
29
CS Coils
30
1 5767698596
0.185
0.265
2 5162647890
0.260
0.365
Service Grids
31
3 3745475968
0.360.51
4 3443445665
0.490.69
Wirewound32
5 2833354349
0.721.01
6 2327293643
0.931.32
7 2024253237
1.241.76
8 1721222732
1.381.97
9 1517192428
2.082.96
10 1215162124
2.783.94
11 1012141821
3.364.75
12 9 11121618
4.235.98
A
E
OVERALL WIDTH
C
B
D
MOUNTING CENTRES
Dimensions (mm)
No of tiers C
4 coils wide 6 coils wide
A
B
254 228
A
B
350 330
ZC5
D
ZC7
E DE
480500 630650
1
125
2
250
3375
29
Technologies
EDGEWOUND
RESISTORS
www.cressall.com
CS coils
Developed for use in bank form the CS
coil is as standard insulated for operation
at 750V, the design is such that this can be
increased to 1.5kV or 3.3kV if required.
CS coil ratings
±10%
Continuous current (A)
for temperature rise of:
Style200°C265°C280°C375°C450°C
DC resistance
(Ω)
(20°C ambient)
CS9 CS12CS15
1 5767698596 0.129
0.172
0.212
2 5162647890 0.182
0.242
0.296
3 3745475968 0.252
0.355
0.415
4 3443445665 0.341
0.455
0.555
5 2833354349 0.505
0.670
0.820
6 2327293643 0.650
0.865
1.060
7 2024253237 0.87
1.15
1.41
8 1721222732 0.98
1.28
1.58
9 1517192428 1.46
1.94
2.36
10 1215162124 1.95
2.58
3.15
11 1012141821 2.26
3.02
3.74
12
911121618 2.84
3.79
4.68
Additional dimensions (mm) for type CS
C: 25mm min.
D: 25mm min.
E: CS9 - 295mm. CS12 - 370mm. CS15 - 445mm.
F: CS9 - 335mm. CS12 - 410mm. CS15 - 485mm.
For 1.5kV primary insulation add 25mm to A & B dimensions.
For 3.3kV primary insulation add 75mm to A & B dimensions
30
No. of elements
A
B
2 250200
3
330 280
4
410 360
5
490 440
6
570 520
7
650 600
8
730 680
9
810 760
10
890
840
SERVICE
GRIDS
www.cressall.com
Service grids
Neutral Earthing
• Modular
contact section to give intermediate tapping
• Shock and vibration resistant
Earth Fault Detection 11
points.
• Range of standard enclosures
• Specifically designed for motor control
6
Every grid has punched holes within the welded
Enclosures
Service grids are a robust flat plate style of
resistor manufactured from 304 grade stainless
steel elements insulated using mica and welded
together to form a continuous low inductance
There are two standard enclosure styles for
service grid resistors; Industrial Housings for
general purpose applications and System 22
Housings designed for steel mills, this allows the
replacement of individual banks without disturbing other banks in the enclosure.
resistance path. Service grid resistors can be
Either type of enclosure can be supplied as
supplied as either open banks or housed in
painted mild steel, hot dip galvanized to BS729
ventilated enclosures.
or natural finish grade 304 stainless steel.
Dynamic Braking
12
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
Edgewound
RP Coils
27
ZO Coils
28
ZC Coils
29
CS Coils
30
Service Grids
Wirewound32
31
Technologies
WIREWOUND
RESISTORS
Coiled wire resistors
A compact and economical solution for high
www.cressall.com
GP resistor data
ments are manufactured using nickel-chrome or
DC Ω
DC Ω
Current ratings for 300°C
GP6/9
±10%
GP12 ±10%
temperature rise (A)
style
@20°C
style
@20°C Contin- Short time rating (secs)
no.GP6GP9
no.GP12
uous
5
10
30
copper-nickel wound onto ceramic formers.
10.130.281
0.41 30 152139114
20.160.362
0.52 27 137125103
30.210.463
0.68 24 120109 90
40.230.524
0.75 23 114104 86
ventilated enclosures, according to customers
50.290.655
0.94 20 102 93 77
requirements.
60.380.846
1.23 18 89 81 67
70.521.107
1.66 15 76 69 57
80.651.408
2.1 14 68 62 51
90.831.809
2.7 12 60 55 45
10 0.94 2.010
3.0
11
56
52
43
11 1.17 2.611
3.8
10
51
46
38
12 1.50 3.312
4.9
9
45
41
34
13
2.0 4.313
6.4
7.7
39
35
29
14
2.3 5.114
7.6
7.2
36
33
27
15
2.8 6.115
9.1
6.5
33
29
25
16
3.6 7.816
11.5
5.8
29
26
22
17
4.2 9.317
13.7
5.3
27
24
20
18
5.1 11.218
16.5
5.1
24
22
18
resistance and low power applications. Ele-
Elements can be supplied either loose, as banked
assemblies or mounted in a range of standard
---
-
32
-----
21
5.7 12.424
18.4
4.9
22
20
15
22
7.5 16.425
24.3
4.5
19
17
13
23 10.3 22.426
33
3.8
16
15
11
24 14.6
3227
47
3.2
14
12 9.44
25 21.7
4728
69
2.6
11
10 7.74
26
27
5929
87
2.3
10 9.03 6.94
27
34
7530
110
2.1 9.08 8.04 6.18
28
44
9631
143
1.8 7.98 7.07 5.44
29
59 12832
190
1.6 6.89 6.11 4.69
30
80 17533
260
1.4 5.92 5.24 4.03
31 105 23034
340
1.2 5.16 4.58 3.52
32 143 31035
460
1.0 4.42 3.92 3.02
33 183 40036
590 0.90 3.91 3.47 2.67
34 240 52037
780 0.80 3.42 3.03 2.33
35 290 64038
950 0.72 3.11 2.75 2.12
36 360 79039
1170 0.65 2.79 2.47 1.90
37 450 99040
1470 0.58 2.49 2.21 1.70
38 580126041
1870 0.51 2.20 1.95 1.50
39 670146042
2170 0.47 2.04 1.81 1.39
40 830180043
2670 0.42 1.84 1.63 1.25
41 1030226044
3360 0.38 1.65 1.46 1.12
42 1320288045
4280 0.33 1.46 1.29 0.99
431740
- -
-0.291.271.120.86
44 2330
- -
- 0.25
453130
- -
-0.210.950.840.64
464650
- -
-0.180.780.690.53
477500
- -
-0.140.610.540.42
1.0 0.97 0.75
www.cressall.com
GP coils
Neutral Earthing
A well proven range of 125 units allows easy
Adjustable tappings can be provided by adding
selection of the most appropriate resistor for
one or more tapping bands.
the duty.
Two types are available, standard and heavy duty,
The coils are manufactured using nickel-chrome
rated for continuous currents of up to 20A and
or copper-nickel alloys wound onto a solid
60A respectively.
ceramic former.
Each tapping band shorts out the resistance wire
Each coil is supported on a flat steel bar which
it covers; the consequent reduction in value of the
passes through the centre of the former and is
overall resistance of the unit is in the range of 1%
secured by spring clips.
to 4%, double for heavy duty tapping bands.
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
Edgewound26
Service Grids
31
Wirewound
GP Coils
33
CC Coils
34
GP stack dimensions
No. of
Width
Mounting No. of
coils overall (mm) centres (mm) tiers
Height
(mm)
1
266
164
1
200
2
344
242
2
351
3
423
321
3
502
4
501
399
4
653
5
580
478
5
804
6
658
556
6
955
7
737
635
7
1106
Unit
A B C DE
8
815
713
8
1257
GP6 194159181 37 53
1408
GP9 257222244 54 68
1559
GP12
356311343 54 68
9
894
792
10
972
870
9
10
GP resistor sizes (mm)
33
Technologies
WIREWOUND
RESISTORS
www.cressall.com
CC coils
The CC coiled coil resistor was developed mainly
for use in dynamic braking. Its open wound coil
arrangement allows operation at up to ten times
its normal power rating for short periods while
retaining quick cooling times.
The CC coil is manufactured from a coil of nickelchrome or copper-nickel alloy wound around a
ceramic former, supported on M8 threaded rod.
Up to three coils can be supported on one rod
allowing easy series and parallel connection and
installation.
CC coil rating
Coil
type
CC8
CC9
Dimensions (mm)
3 wide
4 wide
BD BD
34
No of
tiers
H
1 coil long 260200 260250
1150
2 coils long 440200 440250
2300
3 coils long 630200 630250
3450
Maximum
resistance (Ω)±10%
(@20°C ambient)
Continuous
current, (A) for
600°C temp rise
5.0
10.00
8.0
7.90
CC10
10.0
7.07
CC11
17.0
5.42
CC12
25.0
4.47
CC13
35.0
3.78
CC14
55.0
3.00
CC15
70.0
2.67
CC16
100.0
2.24
CC17
130.0
1.96
www.cressall.com
Neutral Earthing
replacement RESISTORS
Cressall have been producing quality resistors for over 100 years. Our resis-
6
Earth Fault Detection 11
Dynamic Braking
12
Harmonic Filters
18
tors have the reputation for both reliability and longevity. Over the years we
have acquired other resistor companies and have successfully integrated
their technology into our range. In many cases this means we have a library
of technical and contract data to which we can refer.
We hold information on resistors previously supplied under the
following names:
• GEC Alsthom
• GEC Industrial Controls
• Eaton Cutler Hammer
• British Thompson Houston (BTH)
• AEI
• Fawcett Preston
• H. A. Birch
• Expamet
• E. A. Walshe
• BHI
• TPR Resistors
Portable Load Units 20
Static Load Banks
22
Expanded Mesh
24
Edgewound26
Service Grids
31
Wirewound
GP Coils
33
CC Coils
34
We can also supply resistors that can be used to replace our
competitors’ products, this we can do providing we know the rating or the
duty of the resistor involved.
35
Cressall
INDUSTRIAL POWER RESISTORS
Your Local Distributor:
HEAD OFFICE AND FACTORY:
Evington Valley Road, Leicester LE5 5LZ
Tel: +44 116 273 3633
Fax: +44 116 273 7911
SPECIAL PROJECTS AND TRANSIT:
11 Royson Way, Dereham, Norfolk NR19 1WD
Tel: +44 1362 852920
Fax: +44 1362 852921
Issue 4 © 2011 Cressall Resistors Ltd
www.cressall.com